My reverb has started to suffer from a slow and steady air pressure loss. Pumped up to 250psi it’ll lose ~10psi per half hour at first. Below about 100psi the loss rate seems to slow right down as it will be useable the next day but will eventually give up.

Both the post and remote hydraulic systems are fine (remote works fine, there’s no bob in the post).

I’m trying to find the leak, without much success. It’s got to be one of the seals on the (internal) white bit in this diagram, right?

-the two hydraulic systems are fine so it can’t be leaking at the IFP or the orange piston to post oil join
-the seals between the inner seal head (green bit about half way down the post), the air shaft and the inner tube (pink) both look OK on disassembly
-the outer seal between the inner seal head and the stanchion was very slightly pinched when I took apart, but it’s had a fresh one and is still leaking
-the air shaft doesn’t seem to be scratched anywhere
-the air shaft to bottom join looks fine
-all of the last three seals have been cleaned, regreased and reassembled and none show any bubbles when I put a bit of soapy water on them

The last thing I can think of is that the air valve has got tired. That’s the next job if I get time this afternoon, but in the meantime has anyone got any suggestions I’ve missed?

Cheers in advance